Gardeners frequently encounter pupae of various caterpillars while digging in the garden or flower bed and wonder what they have found. While the caterpillars of most butterflies and many moths pupate by forming a chrysalis or cocoon on some above ground structure, such as a leaf or twig, the caterpillars of many other species of moths pupate in the soil. Tomato fruitworm is one of many species of noctuid caterpillars (fall armyworms, cutworms, and yellowstriped armyworms are other examples) that pupate in the soil, and many other species of pest caterpillars, such as tobacco hornworm and squash vine borers, also pupate in the soil.
Once this tomato fruitworm caterpillar was fully mature, it left the tomato it had been feeding in, crawled to the ground, dug several inches into the soil, formed a pupal chamber, and pupated. If this had happened in the summer, the pupal stage would last approximately 10 to 15 days and the resulting moth would emerge and exit the soil to mate and produce another generation. But tomato fruitworms that pupate in late fall enter a state of suspended development known as diapause, and this is the stage in which they spend the winter. The layer of soil helps protect the pupa from freezing temperatures, and the moth will not emerge until next spring. As they dig in to build their pupal chamber, caterpillars form an emergence tunnel, capped by a thin layer of soil, through which the moth can easily exit.
The Bug’s Eye View Newsletter is also entering an overwintering phase. This will be the last regular issue of Bug’s Eye View for 2015. The newsletter will emerge from overwintering and resume publication in March of 2016.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.